[rosswilson]

It's called Insulation Resistance Testing and an electrician would typically use a device like a Megger tester.

Here's a good video about it: https://www.youtube.com/watch?v=CsXUuuV4_sw

[hyperdimension]

Oh, of course. I was not thinking right. I was imagining a 'chunky' HV supply rather than a hi-pot tester, like some Stanford Research PSU, but those only went up to a few kV if I'm remembering correctly. Thanks.